Reflected light type weft monitoring device

ABSTRACT

A device for monitoring a thread, for example the weft thread in a loom of the type in which the weft is driven through the shed of the loom with the aid of a jet, such as a gas jet, for example an air jet, and which has a reed with a longitudinal channel for the weft. An arm with a free end is placed in a position at which it is desirable to monitor the weft. The arm free end has at least one light source for illuminating the monitoring point and any weft located there. A number of light-sensitive elements on the arm free end are aimed towards the channel of the reed to sense the light reflected therefrom. Each light sensitive element generates an electric signal corresponding to the reflected light and is connected to an evaluator circuit for adding the signals regardless of whether the weft at the monitoring point results in an increase or a reduction of the signals obtained from the light-sensitive elements, to generate a signal corresponding to the absolute value of the signals.

FIELD OF THE INVENTION

The present invention relates to a device for monitoring of a thread,for example the weft thread in a loom of substantially the type in whichthe weft is driven through the shed of the loom with the aid of a jet,such as a gas jet, for example an air jet, and which has a reed with alongitudinal channel for the weft and an arm with a free end in aposition at which it is desirable to monitor the arm weft, the free endhaving at least one light source for illuminating the monitoring pointand possibly the weft located there, and a number of light-sensitiveelements.

BACKGROUND OF THE INVENTION

Prior art arrival-indicators function unreliably, often resulting inmany erroneous triggerings, as well as many actual fault triggeringsituations which remain undetected. These problems are particularlyaccentuated in air-driven looms, so-called jet looms, which areextraordinarily rapid and which operate at such high speeds as 20 picksper second, in which event the arrival sensing must be executed underapproximately 10-15° of a whole machine cycle (5% of the cycle). Thisnaturally places extremely high demands on the indicator proper and itsassociated electronics, in particular as regards sensitivity and speed.Moreover, prior art indicators with whose help a part of theabove-outlined problems have been reduced or even wholly obviated haveproved to be extremely uneven in connection with different weft yarns,which may reflect light to different extents. The problems have beenaccentuated in the employment of weft yarns with different colors andstructures. In certain contexts, the problems have proved to be sointractable that no signals have been emitted at all on the use ofcertain weft threads or weft yarns.

SUMMARY OF THE INVENTION

The object of the present invention is to improve the indicators and, tosuch a high degree as is possible, to obviate or at least reduce thesensitivity to different weft yarns or weft threads, both as regardscolor and structure.

This object is solved according to the present invention in that thedevice of the invention is characterized in that the light-sensitiveelements are each aimed in a direction towards the channel for sensingthe light reflected from an illuminated area to generate an electricsignal corresponding to the reflected light, and are each connected toan evaluator circuit for adding the signals regardless of whether theweft occurring in the monitoring point entails an increase or reductionof the signals obtained from the light-sensitive elements. Theillumination of the monitoring point is pulsed to generate a carrierwave with an average amplitude which represents the reflection of lightfrom the channel in the reed and which changes on the occurrence of theweft. The light source and the light-sensitive elements are focusedsubstantially on a line which extends transversely of the channel in thereed. The evaluation circuit includes one channel for eachlight-sensitive element and electronic circuit elements which areprogrammed to treat the signals from the channels, and thereby thelight-sensitive, as absolute value.

The present invention provides a monitoring device which may be employedwith great reliability in the most rapid jet looms or air-driven loomsin that the weft thread is sensed with great dependability regardless ofstructure or colour. A device according to the present invention ismoreover relatively independent of where in the channel the monitoredthread is located. A monitoring device according to the presentinvention moreover obviates the majority of drawbacks inherent in priorart designs and constructions.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in greater detail hereinbelowwith reference to the accompanying drawings.

FIG. 1 is a cross section through parts of a reed including a deviceaccording to the present invention.

FIG. 2 shows, on a larger scale, the encircled portion 2—2 of FIG. 1.

FIG. 3 shows a part of a device according to the present invention fromthe rear.

FIG. 4 shows the part according to FIG. 3 seen from the side.

FIG. 5 shows the part illustrated in FIGS. 3 and 4 from beneath.

FIG. 6 is a perspective view of the part illustrated in FIGS. 3-5.

FIG. 7 shows, on a larger scale, the encircled portion 7—7 in FIG. 6.

FIG. 8 shows an electronic circuit for a first channel in a deviceaccording to the present invention.

FIG. 9 shows an electronic circuit for a second channel in a deviceaccording to the present invention.

FIG. 10 shows an illumination circuit in a device according to thepresent invention.

FIG. 11 shows a circuit for powering parts of the circuits in the deviceaccording to the present invention.

FIGS. 12A-12F when positioned as shown in FIG. 12, show a couplingdiagram of a circuit for evaluating and of the signals from the deviceaccording to the present invention.

DETAILED DESCRIPTION

FIGS. 1 and 2 show parts of a reed which includes a large number oflamellae 1 disposed in spaced apart relationship and extending betweenan upper rail 2 and a lower rail 3. The sectioned part 4 and the nozzle4A are included in the loom. The part 4 serves for guiding the gas jetgenerated by means of a large number of nozzles 4A placed in spacedapart relationship. In this embodiment of a device according to thepresent invention, an arm 5 has a free end in the proximity of thechannel 6 of the reed. At the free end of the arm 5, there is disposedan LED 7 for illuminating the reed channel. The light direction of theLED 7 is illustrated by line 7A in FIGS. 4, 6 and 7. The free end of thearm 5 moreover displays a light-sensitive element 8 in the form of aphoto transistor for sensing reflection from the upper region of thereed channel. The element 8 is directed as illustrated by line 8A inFIGS. 4-7. Further, the free end of the arm 5 has a light-sensitiveelement 9 for sensing reflection from the lower region of the reedchannel and also consists of a photo transistor. The element 9 isdirected as illustrated by line 9A in FIGS. 4-7. Both the LED 7 and thephoto transistors 8 and 9 are focused on a line 10 which extendstransversely of the reed channel 6. The directions are illustrated inFIG. 2 by elements 7, 8, and 9. This may also be expressed such that theelements 8 and 9 are directed at different angles to the channel 6illuminated by means of the LED 7.

The photo transistor 8 is coupled to the electronic circuit illustratedin FIG. 8, and the photo transistor 9 is coupled to the electroniccircuit illustrated in FIG. 9, while the LED 7 is coupled to the circuitillustrated in FIG. 10. The circuit illustrated in FIG. 11 serves forpowering the circuits in FIGS. 8-10. The electronic circuits in FIGS. 8and 9 substantially serve for filtering and amplifying the signals fromthe photo transistors 1 and 2. The outputs from the circuits in FIGS. 8and 9 are coupled to inputs in the evaluator circuit illustrated in FIG.12, whose CPU is programmed to treat the signals from the circuits inFIGS. 8 and 9 in absolute values. The circuit in FIG. 8 is easy torealise for a person skilled in the art with the guidance of thecomponent values included in the diagram. The illumination by means ofthe LED 7 is pulsed for generating a carrier value of average amplitude,which is modified on change of the reflection because of a weft. Theweft may increase the reflection to the first photo transistor 8 andreduce the reflection to the other photo transistor 9, or vice versa.

As a result of the treatment of the signals from the photo transistors 8and 9 in absolute values, the device according to the present inventionwill be insensitive to negative reflection changes in the reed channel,which implies that a change of the reflection from the reed channel isadded regardless of whether the reflection is reduced or increased onthe occurrence of a weft. In this manner, the device according to thepresent invention will be substantially insensitive to wefts ofdifferent colors and structures and, in other words, solves the problemsin those cases when the color and structure of the thread do not entailany major change of the reflection. However, it has proved that thelight-sensitive elements 8 and 9 according to the present invention givesufficient signals for the evaluator circuit in FIG. 12. This circuitmay be realised by a person skilled in the art with the guidance of thecircuit diagram and the component values which may be read therefrom.The various inputs and outputs with the same designation are to beinterconnected (e.g. {circumflex over ( )}P12V and VP12V). The pointsTP1, etc., are test points.

Many modifications of the present invention described in the foregoingare naturally possible without departing from the scope of theinvention.

What is claimed is:
 1. A device for monitoring a weft thread in a loomof the type in which the weft is driven through the shed of the loomwith the aid of a gas jet and which has a reed with a longitudinalchannel for the weft, said device comprising: a light source adapted forilluminating a monitoring position in the channel to monitor the weft atthe monitoring position; a plurality of light-sensitive elements, eachlight-sensitive element adapted to be aimed from a uniquely associateddirection toward the monitoring position to sense light reflectedtherefrom, each light-sensitive element generating an electrical signalindicative of light sensed by such element, an evaluator circuit foradding the electrical signals from said light-sensitive elements toprovide a signal corresponding to the sum of the absolute values of theelectrical signals.
 2. A device as claimed in claim 1, wherein saidlight source is a pulsed light source for generating a carrier wavehaving an average amplitude representing the reflection of light fromthe reed channel.
 3. A device as claimed in claim 1, wherein said lightsource and said light-sensitive elements are adapted to be substantiallyfocused on a line extending transversely of the reed channel.
 4. Adevice as claimed in claim 1, wherein said evaluator circuit includes anevaluation channel for each light-sensitive element, and electroniccircuit elements programmed to treat the signals from said evaluationchannels in absolute value.
 5. A device as claimed in claim 1, furthercomprising an arm having a free end with said light source and saidlight-sensitive elements thereon.
 6. A loom apparatus, comprising: aloom having a shed and a reed with a longitudinal channel for a weft; agas jet for driving the weft through the shed of said loom; a lightsource for illuminating a monitoring position in the channel to monitorthe weft at the monitoring position; a plurality of light-sensitiveelements, each light-sensitive element being aimed from a uniquelyassociated direction toward the monitoring position to sense lightreflected therefrom, each light-sensitive element generating anelectrical signal indicative of light sensed by such element; and anevaluator for adding the electrical signals from said light-sensitiveelements to provide a signal corresponding to the sum of the absolutevalues of the electrical signals.
 7. A loom apparatus as claimed inclaim 6, wherein said light source is a pulsed light source forgenerating a carrier wave having an average amplitude representing thereflection of light from the reed channel.
 8. A loom apparatus asclaimed in claim 6, wherein said light source and said light-sensitiveelements are substantially focused on a line extending transversely ofthe reed channel.
 9. A loom apparatus as claimed in claim 6, whereinsaid evaluator circuit includes an evaluation channel for eachlight-sensitive element, said electronic circuit elements programmed totreat the signals from said evaluation channels in absolute value.
 10. Aloom apparatus as claimed in claim 6, further comprising an arm having afree end with said light source and said light sensitive elementthereon.